The present invention relates generally to a method of counteracting harmful effects of histamine. More specifically, a method of counteracting the harmful effects of histamine by the administration of an antihistaminic substance of Stevia origin having the action of repressing various harmful effects to humans and animals is disclosed.
Recently, pollen has been produced in large amounts by excessive tree planting of Japanese cedars and Japanese cypresses. Moreover, industrialization has increased air pollution or the amount of chemical substances released, so that pollenosis, which is an allergic disease due to combined pollution of the chemical substances and the pollen, has been widely spread. Against such an allergic disease, masks are worn. However, the wearing of masks is only symptomatic therapy, and it is impossible to prevent infection through eyes which cannot be covered with masks.
On the other hand, stevioside and rebaudioside, primarily contained in leaves of Stevia, have a strong sweet taste in small amounts, and are used as natural sweeteners low in calories in substitution for sugar. Stevia is therefore known as a raw material for natural sweeteners low in calories.
As oral drugs antagonistic against histamine, drugs containing antihistaminic agents, such as diphenhydramine hydrochloride and promethazine, are commercially available. However, the antihistaminic agents generally have the side effect of causing drowsiness, which results in a decisive disadvantage when an individual tries to tackle work or to study enthusiastically.
The term "histamine" as used in the present application is intended to be inclusive of histaminic substances, namely, chemical mediators, such as histamine and leukotriene, released from special cells, such as mast cells, as a result of the antigen-antibody reaction, and derivatives of histamine. The derivatives ofhistamine include, for example, dizzerosine produced by elimination of NH.sub.3 from histamine and L-lysine. Excessive release of these substances from the cells and activation thereof causes vasodilatation, which is said to be responsible for flare, itch, and pain.
Antihistaminic substances are known. An example is a Japanese Patent Application No. 7-159971, published in 1996, that teaches that stevioside has an activity suppressing the release of histamine in vivo. Stevioside is the sweet ingredient in leaves of Stevia.
On the other hand, the administration of the Stevia extract of the present invention counteracts the harmful effects of histamine in vivo. Thus, the claimed invention differs from the aforementioned prior art in that the antihistaminic mechanisms are different from one another.
It is desirable to have substances of natural origin for relieving, preventing, and/or curing symptoms of allergic conditions or diseases, which have no side effect such as drowsiness, and which can be continuously applied and/or administered without anxiety of a side effect.